1. Field of the Invention
The present invention relates to a lubrication structure of an engine for reducing the amount of air in the engine oil. The lubrication structure enables a compact layout.
2. Description of the Background Art
Published unexamined Japanese patent application No. 2000-282826 provides a structure wherein oil at the bottom of a crankcase in an oil reservoir is distributed to a transmission case for lubrication through a lead valve accomplished by the rotation of a crank web.
As oil is sucked through a strainer at the bottom of a transmission case and circulated through an engine via an oil pump the distance between the lead valve and the strainer is extended. Furthermore as oil passages between lead valve and the strainer are installed around or near the crankcase, this distance is extended to a greater extent. Therefore, to decrease the weight and decrease the size of an engine by decreasing the size of the lubrication structure, it is desirable that a lead valve and a strainer be brought close together. However, oil sent from the lead valve includes air. It is desirable to prevent the air rich oil from being sucked in through the strainer. Accordingly, the object of the invention is to arrange a lead valve closer to the strainer and preventing air rich oil from being sucked in through the strainer by the oil pump.
The present invention, which has solved the above-mentioned problem, relates to a lubrication structure of an engine comprising a case including a crankshaft, a connecting rod, a piston, and a second case including an oil pan provided at the bottom of the engine. Each case being coupled together via a lead valve. Oil in the oil pan is sucked through a strainer and the exit from the lead valve is separate from the oil pan. A partition for separating air mixed in the oil is provided between the strainer in the oil pan and the lead valve exit.
The sealed case housing the crankshaft, the connecting rod, and the piston and a second case, including the oil pan, are separate. Both cases are connected via the lead valve and the strainer is arranged near the lead valve. Oil that lubricates the crankshaft and the piston is emptied into the oil pan via the lead valve by the reciprocation of the piston. Due to the reciprocation of the piston, oil is prevented from reversely flowing back through the lead valve.
Oil sent from the lead valve includes undesirable air. However, the air can be separated by providing a partition between the exit from the lead valve and the strainer. As a result, a compact layout of the lubricating device, less air in the oil, and the prevention of air from being included in the oil can be accomplished, while decreasing the weight of the engine by decreasing the size of the lubrication structure.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.